My biggest advice, from someone who graduated fairly recently, is to tell the uni. I have a chronic pain condition and depression and told the uni, they were incredible, referred me to their support services, smaller exam room with computer so I wasn't as stressed, offered lockers so I could leave stuff there instead of carrying, provided a laptop and a full desk setup for my accommodation. They worked with me to offer suggestions for things I didn't even think of but that really helped, I know they offer counselling, money advice services, 1-1 support for those that needed it. I had a friend who was dyslexic but wouldn't tell the uni as he wanted to do things himself, it was a lot more difficult although we did what we could to help. They are there to support you, make full use of it, it's what you pay fees for!
Otherwise, he will be fine. You may get a few uncertain or even tearful phonecalls to start with, I felt so homesick even though I loved uni. It was just a big adjustment. Remind him he can tell you anything, no judgement. I still remember my dad dropping everything and driving three hours to pick me up when I had an argument with my friends, knowing they were there for me was everything. I also remember phoning him one day in tears because I failed an essay, he listened while I sounded out solutions and decided what to do. Sometimes that's all you need, someone to help you talk things through, and it sounds like that may be what your son will need most. Knowing he can ring you for any little question and that you will help him through will be a big support.
You sound like an awesome parent. You've got him this far, he will be fine. Let him know you're here any time if he needs you, and if he's struggling. And remind him that if it's not working out, he can always come home. I knew one boy who dropped out first year but stayed in our uni town because he didn't want to tell his parents, got into a lot of debt. I know it may sound counter productive to talk of dropping out at this stage, but just a quiet reminder that it's ok to take some time and maybe go back in a few years may set a few worries to rest if he knows you won't be angry. A few friends considered it at times but worried about what their parents would say. My parents always told me I needed to do what was best for me, and I'm grateful for that.